Method and apparatus for sorting small food items for softness

ABSTRACT

The invention relates to the high speed non-destructive sorting of small food items for softness. The food item is conveyed on a series of belts designed to accurately drop the food item onto a flexible surface at an oblique angle. Accelerometers mounted under the flexible surface generate impact waveforms, which are computer analysed to both detect the item landing position and enable comparison with an operator-selected softness threshold level. Within a few milliseconds of the food item contacting the flexible surface it continues to drop past a rejection point. If determined by analysis to be soft, it is ejected to a waste conveyor.

BACKGROUND OF THE INVENTION

This invention relates to the process of non-destructively sorting small food items by assessment of the condition of softness, particularly for small fruits or vegetables. Small food items are often sorted prior to sale or consumption on the basis of their softness. Products such as blueberries, olives, cranberries, cherries, grape tomatoes, cherry tomatoes require such sorting. There are several mechanical systems used with varying degrees of success. These systems generally use the principle of soft fruit not rolling as freely as firm fruit. This is fairly effective when removing very soft material however it is not very sensitive for a food item that is only slightly soft. This product is often sorted by hand which is labour intensive and can lead to further damage. Very firm fruit such as cranberries are mechanically sorted with a berry bounce system, which is effective however it is often too slow for large-scale packers. Most small fruit grading and packing lines are capable of packing over 5000 lb per hour, which is well beyond the capacity of the cranberry bounce softness sorter.

The main reason for wanting to sort out the soft food items is to increase the product shelf life. The soft product tends to have a higher incidence of rots and decay. Softness can also be a function of maturity, and over maturity can also contribute to reduce shelf life. Such food items are also commonly subject to pricing regimes that are product-quality dependent, so to match product quality to market expectations usually results in maximising returns to the product owner.

To address the quality matching issue, a product sorter is described. Any symmetrical food item within a size range similar to a berry can be sorted on the basis of its softness using this method and apparatus. Other food items may also be suitable, provided the fall involved in its characterisation is insufficient to create tissue damage causing subsequent susceptibility to premature quality degradation. The preferred embodiment of the invention utilises a shallow angle rebound (ricochet) so as to minimise the deformation energy imparted to the food item during rebound, thereby minimising risk of tissue damage, while yet being sufficient to extract its ricochet energy signature.

This invention is superficially similar in principle to U.S. Pat. No. 6,541,725 (Acoustical apparatus and method for sorting objects) in which the procedure of rebounding a food item off a surface is optimised for hard items such as nuts, which emit an acoustic deformation energy signature after leaving the impact surface. That technique requires a rigid and immovable rebound surface, and the introduction of a time delay after the impact to ensure the deformation energy signature is sampled at the appropriate time after rebound. Additionally, the deformation energy is released by acoustic radiation in air, therefore appropriately detected by microphone. In contrast, this invention extracts the deformation energy signature by conducted energy transfer while the food item impacts a resiliently mounted rebound surface and remains in contact with that surface. In this aspect its detection method is similar to a cherry sorter impact sensor (Younce & Davis, 1995, ASAE) but necessarily and fully integrates impact trajectory control into its functioning.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an elevation of an exemplary embodiment of the invention, illustrating the trajectory of a food item of softness less than the threshold value.

FIG. 2 shows the trajectory of a food item of softness greater than the threshold value, and its diversionary means.

FIG. 3 shows the exemplary embodiment in plan view, and illustrating the conveyor belt profile.

DETAILED DESCRIPTION OF THE INVENTION

The invention comprises both a method and apparatus for sorting small food items for softness, which: accurately projects 2 a food item 1 onto a target plate 3, obtains a measurement of food item softness from instrumentation (not shown) associated with the target plate 3, generates an accept/reject decision based on the comparison between the measured softness and a pre-selected decision threshold, to either during ricochet trajectory 5 allow the food item 1 to remain in the flow of accepted items 6, or if required, during ricochet trajectory 9, actuate a rejection procedure 10 to divert 11 the food item 12 to waste.

The apparatus comprises a target trajectory control system (not shown), in which the horizontal plane alignment for target accuracy is determined by a system of moveable belts 13; the belts function as a sequencing conveyor to deliver food items 1 to a target 3 one at a time; the sequencing conveyor belts are of special inverted V shape, in which the belt shape improves food item trajectory 2 control in the horizontal plane; the horizontal plane trajectory control improvement results from belt profile change consequent on flexure during passage around a pulley (not shown); the vertical plane target trajectory 2 control is achieved by a combination of mechanical and electronic and computational means; the vertical plane target trajectory 2 control is achieved by varying the moveable belt 13 velocity by a variable speed drive system (not shown); the vertical plane target trajectory 2 control system achieves consistent targeting accuracy by varying the inverted V belt velocity under control by averaged data feedback derived from the impact analysis system.

An impact analysis system, comprising an instrumented target plate 3, and associated electronic signal processing and control system hardware and software (not shown), in which the instrumented target plate 3 comprises a resiliently mounted rigid plate containing multiple accelerometers; each accelerometer generates electrical signals representing the food item softness; purpose-designed but otherwise conventional electronics amplify and convert the signals to digital form; purpose-designed but otherwise conventional software operating on a conventional digital signal processor system extracts real-time data from those digitised signals; the real-time data from each accelerometer pair on an impact plate 3 is compared; the real-time data is analysed for magnitude of initial reverse-phase signal generated by off-centre impact; analysis of the signals generated during target impact is transformed into numbers representing food item softness; the softness data is compared with the selected softness threshold and thereby transformed into a decision to accept (see FIG. 1) or reject (see FIG. 2) the food item; from the reverse-phase data is generated an “item off-centre” data value which, averaged over a short time period, is transformed into a feedback signal to influence said sequencing conveyor velocity to maintain target accuracy; that feedback signal is converted into a variable delay 4 influencing air jet timing; the averaged real-time data is supplied to adjacent impact analysis systems (not shown) enabling the modification of their analytic parameter settings.

A soft food item rejection system, in which a soft food item 12 is ejected during ricochet 9 from the said target plate 3 by pneumatic means 7, 8, 10; the pneumatic means is a conventional electrically controlled pneumatic actuator 7 supplied with high pressure air 8; said pneumatic actuator 7 releases a high velocity air jet 10 if the food item is identified as above the selected softness threshold; the air jet 10 accelerates 11 the food item 12 towards a reject conveyor (not shown) of conventional design.

A system of output conveyors (not shown) of conventional design to collect selected food items, food item debris, and rejected food items.

An operator interface (not shown) of conventional design, in which numeric softness data may be displayed; the softness selection threshold may be adjusted; other operator commands may be input; and all other analytic results may be accessed. 

What is claimed is: 1) A method and apparatus to measure and selectively divert near-spherical food items into two streams from a single stream, wherein the measurement of each food item's softness is by analysis of its ricochet energy signature. 2) A method and apparatus as claimed in claim 1, wherein the ricochet energy signature analytic surface constitutes an instrumented target containing force measuring devices to convert the ricochet energy signature into a computed decision to accept or reject that food item. 3) A method and apparatus as claimed in claim 2, wherein the measurement method employs accelerometers as the force measurement devices. 4) A method and apparatus, substantially as described and illustrated in FIGS. 1-3, primarily employing a measurement method to evaluate the condition of softness of a food item and secondarily to use the measurement method to maintain targeting accuracy of the object to be measured. 